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staging:iio:dac:ad5791: Allow asymmetrical reference voltages

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The ad5791 currently assumes that the negative and positive supply have the
same absolute value, which is not necessarily true. This patch introduces a
offset attribute which will contain the negative supply voltage scaled
according to the iio spec. The raw attribute now accepts values in the range
of 0 to max instead of -max/2 to max/2.

While we are at it also fix the vref span calculation. Since both positive and
negative reference voltages are specificed as absolute values we need to add
them and not subtract them to get the reference voltage span.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Lars-Peter Clausen 2011-10-19 17:47:50 +02:00 committed by Greg Kroah-Hartman
parent 021c0a381c
commit 9dc9961dca
2 changed files with 18 additions and 8 deletions
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24
drivers/staging/iio/dac/ad5791.c
View File

@ -77,7 +77,8 @@ static int ad5791_spi_read(struct spi_device *spi, u8 addr, u32 *val)
.indexed = 1, \
.address = AD5791_ADDR_DAC0, \
.channel = 0, \
.info_mask = (1 << IIO_CHAN_INFO_SCALE_SHARED), \
.info_mask = (1 << IIO_CHAN_INFO_SCALE_SHARED) | \
(1 << IIO_CHAN_INFO_OFFSET_SHARED), \
.scan_type = IIO_ST('u', bits, 24, shift) \
}
@ -225,6 +226,7 @@ static int ad5791_read_raw(struct iio_dev *indio_dev,
long m)
{
struct ad5791_state *st = iio_priv(indio_dev);
u64 val64;
int ret;
switch (m) {
@ -234,12 +236,16 @@ static int ad5791_read_raw(struct iio_dev *indio_dev,
return ret;
*val &= AD5791_DAC_MASK;
*val >>= chan->scan_type.shift;
*val -= (1 << (chan->scan_type.realbits - 1));
return IIO_VAL_INT;
case (1 << IIO_CHAN_INFO_SCALE_SHARED):
*val = 0;
*val2 = (st->vref_mv * 1000) >> chan->scan_type.realbits;
return IIO_VAL_INT_PLUS_MICRO;
case (1 << IIO_CHAN_INFO_OFFSET_SHARED):
val64 = (((u64)st->vref_neg_mv) << chan->scan_type.realbits);
do_div(val64, st->vref_mv);
*val = -val64;
return IIO_VAL_INT;
default:
return -EINVAL;
}
@ -257,7 +263,6 @@ static int ad5791_write_raw(struct iio_dev *indio_dev,
switch (mask) {
case 0:
val += (1 << (chan->scan_type.realbits - 1));
val &= AD5791_RES_MASK(chan->scan_type.realbits);
val <<= chan->scan_type.shift;
@ -309,12 +314,15 @@ static int __devinit ad5791_probe(struct spi_device *spi)
st->pwr_down = true;
st->spi = spi;
if (!IS_ERR(st->reg_vss) && !IS_ERR(st->reg_vdd))
st->vref_mv = (pos_voltage_uv - neg_voltage_uv) / 1000;
else if (pdata)
st->vref_mv = pdata->vref_pos_mv - pdata->vref_neg_mv;
else
if (!IS_ERR(st->reg_vss) && !IS_ERR(st->reg_vdd)) {
st->vref_mv = (pos_voltage_uv + neg_voltage_uv) / 1000;
st->vref_neg_mv = neg_voltage_uv / 1000;
} else if (pdata) {
st->vref_mv = pdata->vref_pos_mv + pdata->vref_neg_mv;
st->vref_neg_mv = pdata->vref_neg_mv;
} else {
dev_warn(&spi->dev, "reference voltage unspecified\n");
}
ret = ad5791_spi_write(spi, AD5791_ADDR_SW_CTRL, AD5791_SWCTRL_RESET);
if (ret)

2
drivers/staging/iio/dac/ad5791.h
View File

@ -82,6 +82,7 @@ struct ad5791_chip_info {
* @reg_vss: negative supply regulator
* @chip_info: chip model specific constants
* @vref_mv: actual reference voltage used
* @vref_neg_mv: voltage of the negative supply
* @pwr_down_mode current power down mode
*/
@ -91,6 +92,7 @@ struct ad5791_state {
struct regulator *reg_vss;
const struct ad5791_chip_info *chip_info;
unsigned short vref_mv;
unsigned int vref_neg_mv;
unsigned ctrl;
unsigned pwr_down_mode;
bool pwr_down;